Use -fsanitize-recover instead of -mllvm -msan-keep-going: clang.

Summary: Use -fsanitize-recover instead of -mllvm -msan-keep-going: pass -fsanitize-recover value to msan.

Reviewers: eugenis

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26354

Patch by Aleksey Shlyapnikov.

llvm-svn: 286148